1. Field of the Invention
This invention relates to textured film and articles made therefrom, and to a method of treating such film to enhance the elastic and/or extensibility characteristics thereof. In a specific embodiment, the invention relates to condom articles formed of thermoplastic elastomeric film which has been textured to enhance its elastic properties.
2. Description of the Related Art
In recent years, there has been a significant increase in the incidence and spread of sexually transmitted diseases (STD's). This phenomenon has in turn caused an increased use of condoms as a prophylactic measure to reduce the risk of infection and transmission of such diseases.
Among the reasons for the increase in incidence and rate of transmission of STD's are the development of increasingly antibiotic-resistant strains of disease-causing organisms, e.g., those responsible for diseases such as syphilis and gonorrhea. Another factor has been the absence of any effective cure for acquired immunodeficiency syndrome (AIDS).
The diseases with which AIDS has been or is suspected to be linked include Pneumocystis carinii pneumonia, Kaposi's sarcoma, esophageal or bronchopulmonary candidiasis, extrapulmonary cryptococcosis, cytomegalovirus internal organ infection, disseminated Mycobacterium avium complex or M. kansasii infection, chronic herpes simplex ulceration, chronic cryptosporidiosis enteritis, toxoplasmosis of the brain, high-grade B-cell non-Hodgkin's lymphoma, disseminated histoplasmosis, chronic isosporiasis enteritis, and lymphoid interstitial pneumonia in children.
Against the foregoing background, and the recognition that condoms afford a safe, low cost, and generally reliable means for combatting the spread of STD's, including AIDS, there has been an increased demand for condoms.
Currently, most condoms are produced from a latex resin via a dipping process in which a cylindrical and rounded-end mold is dipped into a resin bath, so that the mold is coated with a thin layer of the latex material. The thickness of the latex coating on the mold is dependent on the viscosity of the latex, and the speed of extracting the mold from the latex- bath. Similar latex dipping processes have been employed with suitably shaped molds to form tight-fitting gloves such as surgical gloves.
The above-described latex resin dipping process has been utilized for decades, and yields a generally satisfactory barrier product at reasonable cost.
With the recent spread of AIDS in the general population and the resurgence of condom usage in sexual activities, there has been interest in improving the strength and reliability characteristics of condoms, and of achieving improvements in manufacturing processes and economics, to further combat the spread of STD's generally, and AIDS specifically, as well as to provide a safe and reliable contraceptive means.
As indicated above, the thickness of conventional latex condoms is dependent on the viscosity of the latex in the mold dipping bath, and the speed of extraction of the mold from such bath. As a result of such viscosity and processing rate dependence, latex condoms generally are characterized by variations in thickness, which are usually acceptable, but which introduce variable material requirements into the manufacturing process.
Consideration has been given in the art to the possibility of using synthetic film materials for condom manufacture, to take advantage of mass production techniques and the high uniformity of thickness and material properties which are typical of most commodity polymeric films. In order to accommodate the requirement of relatively low thickness of the condom material, and the concomitant need for strength and stability in such material in order to maintain the structural integrity of the condom during its processing, storage, and subsequent use, attention has specifically been given to potential utilization of synthetic elastomeric polymer films as condom materials.
In respect of its physical properties, latex rubber has the advantage that it generally has a significantly lower modulus of elasticity as compared to synthetic elastomeric polymer films.
Nonetheless, synthetic elastomeric polymer films have significant potential advantages in use as a condom material of construction, particularly thermoplastic elastomeric materials, because of their ready formability, availability, and low cost, and their physical, chemical, and mechanical properties, including low porosity.
It therefore would be a significant advance in the art to provide a condom which is fabricated from a thermoplastic elastomeric material which exhibits the generally favorable properties of synthetic elastomeric films, but additionally is characterized by a reduced modulus of elasticity, such that the condom material more closely approximates the elastic properties and textural characteristics of natural latex rubber.
U.S. Pat. No. 4,574,156 issued Mar. 18, 1986 to Manfred F. Dyke discloses a condom formed of a thermoplastic polyurethane material, having a generally cylindrical configuration with an open proximal end and a closed distal end. The disclosed condom has a thickness of from about 0.01 millimeter, or less, to about 0.25 millimeter. The thermoplastic polyurethane employed to form the condom is disclosed as having: an average Shore A hardness of from about 50 to about 90; a tensile stress, at 100% elongation, between about 300 and 1,000 psi; and a tensile stress, at 300% elongation, between about 800 and 3,000 psi. Suitable thermoplastic polyurethane species for manufacturing the condom include those set out at column 2, line 55 to column 3, line 10 of the Dyke patent, with polyether- or polyester-based urethane elastomers said to be preferred. In the manufacture of the thermoplastic polyurethane condom disclosed in the Dyke patent, a film of the polyurethane material, e.g., in the form of a 6-inch square, is heated to a temperature high enough to soften the polymer but low enough to avoid chemical degradation, preferably in a clamping frame, and at a temperature of about 400.degree.-500.degree. F. The heated film then is brought into contact with a preformed mandrel to cause the film to assume the shape of the mandrel, preferably with application of a vacuum to the system in order to bring about uniformity in wall thickness (column 3, lines 47-50 of the patent).
European patent application 0 147 072 published July 3, 1985 in the names of Robert A. Taller, et al., discloses a process for making a polyurethane condom with a uniform thickness of from about 1.5 to about 4 mils. A heat-curable polyurethane prepolymer solvent solution is employed into which a mold is dipped and withdrawn for subsequent heat curing on the mold. The polyurethane prepolymer which is employed in the dipping medium is a prepolymer which is the reaction product of a polyisocyanate with at least one long-chain polyol. The polyol is amorphous at room temperature, has an average molecular weight of from about 500 to about 5,000, a hydroxy number of from about 225 to about 22.4, and an NCO/OH ratio of from about 0.95:1 to about 1.1:1.
U.S. Design Patent 253,009 to T. Okamoto shows a prophylactic device whose frontal (distal) section comprises a pair of indented surface portions forming circumferential grooves in the prophylactic, transverse to the longitudinal axis thereof.
U.S. Pat. No. 4,964,416 issued Oct. 23, 1990 in the names of Robin G. Foldesy and Robert G. Wheeler discloses a variety of condom configurations which are fabricated of thermoplastic materials such as thermoplastic elastomeric materials, and non-elastomeric materials such as olefinic homopolymers and copolymers, e.g., ultra-low-density polyethylene.
It therefore is an object of the present invention to provide films having enhanced elasticity and/or extensibility characteristics, such as may be usefully employed in the fabrication of condom articles.
It is another object of the invention to provide a method of treating a film material to enhance the elastic properties thereof and render it highly advantageous for applications such as condom articles.
Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.